1. Field of the Invention
The present invention relates to a composition and process for recovery of spilled hydrocarbons from aqueous environments and surrounding structures, and more particularly, by use of a polymer composition.
2. Description of the Related Art
The recovery of unwanted material, such as spilled hydrocarbons on water, sand or other structures, has been an environmental concern for many decades. Oil spilled or leaked from tankers, vessels, docks and offshore wells are just a few of the many examples that continue to threaten our environment. Spills and leaks create havoc with birds and other wildlife that inhabit the water and surrounding areas. As long as the demand for petroleum products exists, spills and leaks will continue to occur thus requiring prompt attention and clean up.
Oil spills and leaks occur on bodies of water of all types, including those containing fresh, brackish, or salt (sea) water. Recovery of oil may also be required on beaches and coastal lands. In yet other situations, it may be required to recover oil from a source, such as the side of a vessel. The unwanted material may be any hydrocarbon material, including, but not limited to, crude oil, residual fuel oils, and distilled products such as gasoline, kerosene-type jet fuel, diesel fuel, heating oil, etc. The term “oil spill” is used herein to refer to a pool or mass of oil floating on a body of water, and without distinction as to the source of the oil or the manner in which it was released.
Several processes and techniques have been used in the past to facilitate the clean up of oil spills. One such technique has been to use polyurethanes to recover spilled hydrocarbons.
U.S. Pat. No. 3,869,385 discloses spraying formulations suitable for making polyurethane foam on water or sand in order to remove oil. The '385 patent discloses a process for containing oil spills on bodies of water by applying a polyisocyanate and a polyamine to the oil spill. The resulting polymer forms a rubbery gelled mass to contain the oil by a thickening or coagulating effect.
U.S. Pat. No. 4,980,072 discloses the use of an isocyanate-terminated prepolymer for removing hydrocarbons, in particular oil, by preparing a gel. The disclosed prepolymer has an NCO value of 4.2% by weight which has been made from toluene diisocyanate and a polyether polyol which has been tipped with about 2% by weight of propylene oxide. The '072 patent further discloses that the prepolymer may be mixed with water before bringing the prepolymer into contact with the oil. In the examples, the prepolymer is combined with water and thoroughly mixed for 25 seconds before it is combined with the oil. It is believed that this premixing with water is conducted in order to achieve a certain degree of pre-reaction of the prepolymer and the water. It is further believed that without such a long mixing time, which under field conditions would be unpractically long, only unrecoverable crumbs would be obtained.
EP-415127 discloses the use of prepolymers as flocculating agents.
Application PCT/EP95/01517 discloses the use of a prepolymer, made from 4,4′-diphenylmethane diisocyanate (4,4′-MDI) and a polyol having an oxyethylene content of 50-85% by weight, for removing oil spills from water. It further discloses that the prepolymer may be brought into contact with the oil and water as a froth obtained by adding water to the prepolymer.
U.S. Pat. Nos. 5,504,124 and 5,730,880 disclose a process for removing oil from water by bringing an isocyanate-containing prepolymer into contact with the oil and water, and allowing the prepolymer to react with the water to form a flexible foam. The flexible foam with the oil is then removed from the water. The '880 patent discloses that the process for removing oil from water by using a prepolymer may be further improved by adding a certain amount of water to the prepolymer a few instants before the prepolymer is brought into contact with the oil/water. The '880 patent further discloses that use of the water: reduces the viscosity of the prepolymer and changes the surface tension to make it easier to apply the prepolymer to the oil and water; provides adequate spraying patterns (fine droplets), especially when the prepolymer and the water are mixed in a spraying gun; and produces a sufficiently high output of the prepolymer from such a spraying gun whereas without this water the output is low and the prepolymer leaves the nozzle of the gun as a jet-stream. The flexible foam, obtained after the prepolymer and water mixture have been combined with the oil and water, retains the oil very well after the foam has been removed from the water surface. The '880 patent further states that because the water is added to the prepolymer only a few instants before the prepolymer is brought into contact with the oil and water no noticeable pre-reaction takes place, particularly not when the water is applied at a temperature of 5°-35° C.
The prepolymer composition disclosed in the '880 patent is very difficult to use commercially, particularly in oil spill clean-up operations, as it is very hydroscopic and reacts quickly with moisture. As a result, dispensing systems developed for the prepolymer composition disclosed in the '880 patent could only be used one time and then had to be dismantled, cleaned and reassembled for subsequent use. Such problems have created extreme difficulties in commercially exploiting the prepolymer composition of the '880 patent. The current applicants witnessed these problems firsthand in a demonstration of the dispensing equipment following the method of spraying the mixed product as suggested in Examples 3 and 4 of the '880 patent, column 5, lines 15-32.
Assignee's U.S. Pat. No. 5,723,534 discloses the use of prepolymers in a two-part adhesive. The '534 patent incorporates the use of an isocyanate-terminated prepolymer as one component of a two-part adhesive system utilizing the hydrophilic characteristic of the prepolymer to initiate reaction of the polyurethane/latex bond.
The viscosity of the prepolymers produced from the aforementioned prior art patent disclosures is extremely high, in the range of 10,000 to 20,000 centipoises, which restricts the commercial application and use of the technology. It is desirable to have a prepolymer with a lower viscosity to enhance the commercial application and use of the technology.
It is also desirable to have a commercially viable, practical, reliable, inexpensive delivery system for applying a hydrocarbon sorbing and/or encapsulating, foamable, flexible polyurethane foam on the surface of contaminated water and surrounding structures.